1. Field of the Invention
This invention relates to pumps for washing liquid in dishwashing apparatus and, more particularly, to structure for selectively controlling the delivery of washing liquid from said pump through separate conduits.
2. Description of the Prior Art
A complete operating cycle for conventional dishwashing apparatus includes at least one rinsing cycle wherein washing liquid is forcibly delivered into a wash chamber. The washing liquid is collected and recirculated until the rinsing cycle is completed after which the washing liquid is forcibly delivered into a suitable drain and directed away from the apparatus.
It is known to selectively propel washing liquid through conduits into the wash chamber and drain by separate, independently operable pumps. It is also known to use a bidirectional pump which, when operated in a first direction, directs washing liquid into the wash chamber and, when operated in a direction opposite to the first direction, discharges the washing liquid through the drain. Normally, the latter type structure requires valving to prevent inadvertent passage of washing liquid through one of the conduits when the flow is intended to be principally through the other conduit.
An exemplary structure is shown in U.S. Pat. No. 2,838,002, to Cohen. In Cohen, separate, deflectable, flap-like valves are anchored in the vicinity of each of the conduits. Rotation of the pump in one direction bends one valve over its associated outlet and urges the other valve away from a sealing position. Reversal of the pump rotation produces an opposite effect on the valves.
As an alternative to the Cohen structure, in U.S. Pat. No. 2,883,843, to Bochan, a single valve member is hinged for pivoting movement between two positions wherein transverse surfaces on the valve member sealingly close conduit openings. As with the Cohen structure, the valve is directly impacted by the liquid flow and is manipulated thereby.
The Cohen and Bochan structures have several drawbacks. First of all, the structures are relatively complicated. Further, for the valve elements to pivot freely, a hinge portion must be incorporated that can be easily deformed. Such structures are inherently susceptible to failure. Still further, the valve in each of Cohen and Bochan must pivot through a substantial range of motion. In the event that foreign matter accumulates in the path of the valves, the operation of the valves might be imparied and the seal at one or both of the conduits compromised.
It is also known to use solenoid valves to effect the aforementioned flow conversion. Alternatively, in U.S. Pat. No. 3,633,622, to Ralston, there is incorporated a bimetal control for a valve. The Ralston valve control as well as those incorporating solenoids, are relatively involved. This complicates manufacturing and increases the attendant costs thereof. Further, the more complicated the structure, the greater the likelihood of failure.